For example, the ISO standard family 11898-1 through -5 describes the Controller Area Network (CAN) as well as an extension of the CAN called “time-triggered CAN” (TTCAN), referred to in the following also as standard CAN. The media access control method used in the CAN is based on a bit-wise arbitration. In bit-wise arbitration, multiple subscriber stations are simultaneously able to transmit data via the channel of the bus system, without thereby interfering with the data transmission. Furthermore, the subscriber stations are able to ascertain the logical state (0 or 1) of the channel while transmitting a bit over the channel. If a value of the transmitted bit does not correspond to the ascertained logical state of the channel, the subscriber station terminates the access to the channel. In CAN, the bit-wise arbitration is usually carried out on the basis of an identifier within a message that is to be transmitted via the channel. After a subscriber station has sent the identifier to the channel in its entirety, it knows that it has exclusive access to the channel. The end of the transmission of the identifier thus corresponds to a beginning of an enable interval, within which the subscriber station is able to use the channel exclusively. According to the CAN protocol specification, other subscriber stations may not access the channel, that is, send data to the channel, until the sending subscriber station has transmitted a checksum field (CRC field, CRC field, “CRC checksum”) of the message. Thus, an end point of the transmission of the CRC field corresponds to an end of the enable interval. A further property of the protocol specification is that, after, in each case, five bits having the same value, an additional, so-called “stuff bit” having an opposite value is inserted into the data flow by the sender, in order to ensure the appearance of signal edges which are required for the synchronization of the bus subscribers, particularly sampling points. The inserted “stuff bits” are discarded again on the receiver side. They are not subject to the CRC checking mentioned above.
Because of the protocol, thus, a non-destructive reliable transmission is achieved of that message via the channel that has won the arbitration process. The CAN protocols are particularly suited for transmitting short messages under real-time conditions, a suitable assignment of the identifiers being able to ensure that particularly important messages will almost always win the arbitration and be sent successfully.
Because of the transmission of a CRC field formed from the data transmitted before in the message, using a generator polynomial, and carrying out a CRC checking on the receiver side, a high transmission reliability or error detection reliability is yielded. The insertion of so-called stuff bits at places within the message, at which five successive, equal bits are transmitted, in connection with the resynchronization of the bit timing, with the aid of edges between the bits having a different value, ensures a high tolerance with respect to the oscillators used.
With the increasing networking of modern vehicles and the introduction of additional systems for improving driving safety, for example, or driving comfort, the demands grow on the quantities of data to be transmitted and the latency periods admissible in the transmission. Examples are driving dynamics control systems such as e.g. the electronic stability program ESP, driver assistance systems such as e.g. the automatic distance control ACC, or driver information systems such as e.g. the traffic sign detection (cf. for example descriptions in “Bosch Kraftfahrtechnisches Handbuch” (“Bosch Automotive Handbook”), 27th edition, 2011, Vieweg+Teubner).
G. Cena and A. Valenzano, in “Overclocking of controller area networks” (Electronics Letters, vol. 35, No. 22 (1999), p. 1924) deal with the effects of overclocking the bus frequency in subsections of the messages on the effectively achieved data rate.
The document “CAN with Flexible Data-Rate, White Paper, Version 1.0”, published on May 2, 2011 on Internet page http://www.semiconductors.bosch.de/, introduces a modified data transmission protocol which, among other things, enables an enlargement of the data field as well as a shortening of the bit length for a part of the CAN message. Stuff bits that appear before the beginning of the CRC field are included in the CRC checking in CAN FD, which already leads to a higher data integrity. However, stuff bits appearing within the CRC field are further exempted from the CRC checking. This represents a limitation for the reliability of the error detection mechanisms of the protocol. It is clear that the related art does not provide results that are satisfactory in every respect.